TNG inspires me. It's like the Jurassic Park theme, or The White Tree theme from LotR, or Corridors of Time from Chrono Trigger. Stories where the smartest people you've never met get together to do something capital-G Great. There's conflict and drama and things aren't perfect, because there are always these things, but at least there's ambition.
TOS was pretty okay. I never got that much into it— I saw the "pon farr" episode and thought it was pretty dumb how Spock failed to mention that a little mortal combat would be involved. Whoops! Silly mistake; could happen to anybody. I still need to check out the animated series, because everyone says it was awesome.
DS9 was cool because of all the intrigue and black-and-gray morality that comes with mass-scale conflict. I don't have much nostalgia for it, but I get why people do. Come to think of it, there was a dude on youtube back in 2010 who uploaded an episode each day, and a bunch of people would be in the comments afterward to discuss it. Turned into a bit of a book club. There was the one guy who always said O'Brien was a "pimp." A real chad; a pussy-magnet, that O'Brien. I remember making fun of how he, the chief engineer, would struggle to spit out his treknobabble. I'm nostalgic for that.
VOY was more like a road-trip with your rowdy aunt, and there are a lot of themes I found detestable, like "holograms are people and they should have rights and wah wah wah." Like, cool, let me just spin up my Amazon servers and fabricate a trillion "people" ahead of the next election, lmao. Stupid as hell, risible throughout. At least there was Seven of Deez Nutz in the later seasons.